The heating and cooling of structures can be accomplished in a variety of ways, using a variety of primary systems which include a variety of primary equipment. There are other systems and other equipment which are designed and arranged to provide supplemental heat transfer which may be either heating or cooling. The specific nature of the heat transfer, including the transfer direction, depends on whether supplemental heating or cooling is the intended objective of the heat transfer. In the context of the exemplary embodiment of the present invention the referenced structures are selected to be residential structures. One such supplemental heat transfer system utilizes geothermal heat transfer either to or from the earth's mass as the selected heat sink. Circulation of a heat transfer fluid through the geothermal heat transfer system (flow conduits or piping buried at a desired depth) results in the following forms of heat transfer.
In the warmer months a warmer fluid exits from the residential structure, building, house, etc. and flows or circulates through the geothermal system with the earth's mass, at the operating depth of the system, being at a lower temperature. This temperature difference results in heat transfer from the cooler earth's mass. Accordingly, the circulating fluid re-enters the residential structure at a lower temperature than when it left the residential structure.
In the cooler months a cooler fluid exits from the residential structure and flows or circulates through the geothermal system with the earth's mass, at the operating depth of the system, being at a higher temperature. This temperature difference raises the temperature of the circulating fluid such that the circulating fluid re-enters the residential structure at a higher temperature than when it left the residential structure.
In order to visualize the above and understand the heat transfer which is able to occur, consideration of some relative numbers, as but one example, may help. These relative numbers are for example only and while they may be close to the actual temperatures, these numbers are simply for reference. In this regard, assume an earth mass temperature at a 6 foot depth of 70 degrees F. Next assume that in the warmer months the warmer fluid exiting the residential structure is at 90 degrees F. This 20 degree difference results in heat transfer from the circulating fluid thus lowering the temperature of the circulating fluid before its re-entry into the residential structure. In the cooler months, still using reference numbers for example only, assume that the exiting fluid is at 60 degrees F. Assume further that the earth mass temperature at a 6 foot depth is still 70 degrees F. This 10 degree difference results in heat transfer to the circulating fluid thus raising the temperature of the circulating fluid before its re-entry into the residential structure.
The geothermal heat transfer system described above is not limited to the heating and cooling of any particular circulating fluid. The heat transfer principles described above which are associated with a geothermal system are applicable to any setting or environment where there is an available heat sink which provides a generally stable temperature which is within the likely range of heating and cooling temperatures to be expected, such that heat transfer will occur. One concern for any heat transfer system which is to be installed for use with a residential structure is the cost. There are equipment costs and installation costs. These costs need to be considered relative to the energy savings to be expected by the owner.
Based on the above system description, it is envisioned that there are two areas for improvement in the supplemental heating and cooling of residential structures. One area for possible improvement is directed to finding a suitable heat sink with a generally stable temperature within the range for cooling heat transfer in the warmer months and for warming heat transfer in the cooler months. Another area for possible improvement is directed to finding construction short cuts which provide cost-cutting techniques for the builder when the residential structure is being constructed.
The present invention provides an improvement in the design and construction of a supplemental heat transfer arrangement for use in conjunction with a geothermal system. A further improvement is provided as part of the original construction such that the supplemental heat transfer arrangement is able to be installed when the geothermal system is being installed. More specifically, the present invention is directed to the integration of a pressure sewer wastewater discharge system and a geothermal loop as further explained below.
The wastewater discharged from a residential (or light commercial) building is a potential source of renewable, low grade energy suitable for use with compression based HVAC heating and cooling and domestic hot water heating. Recent technology advances in pressure sewer (pumped wastewater discharge, not gravity sewer discharge) applications for the sewer lateral piping joining a building to the municipal sewer collection system using horizontal boring technology offers an opportunity for a design improvement. More specifically it offers a way to couple a closed loop geothermal piping system with the pressure sewer wastewater discharge lateral piping using the surrounding soil to provide a renewable energy boost to the geothermal loop heat transfer capacity.
The typical temperature of the wastewater contained in the in-ground storage tank in the Midwestern United States is approximately 70 degrees F. In the cooling mode during the summer months, typical discharge temperatures off of the condenser to the geothermal loop are approximately 90 degrees F. In summer months when cooling is required, the wastewater fluid contained in the pressure sewer lateral will absorb heat from the surrounding soil and geothermal loop, raising the temperature of the wastewater while lowering the temperature of the geothermal cooling loop.
As the wastewater flows into the branch and main collection system lines, this heat will be rejected into the cooler soil surrounding the piping until the wastewater temperature reaches an equilibrium with the surrounding soil temperature. During the winter months the heat in the approximately 70 degrees F. pressure sewer discharge wastewater will be rejected into the cooler surrounding soil and the geothermal fluid in the pipe will leave the evaporator at approximately 60 degrees F. and below. Therefore the pressure sewer discharge wastewater will help raise the temperature and increase the efficiency of the geothermal loop and compressor based heating system. During the coldest winter months an auxiliary heating source or boiler system may be required to add heat to the geothermal loop fluid before it enters the evaporator to provide entering temperatures required for the compression based heating system.
The present invention takes a holistic approach to the integration of in-ground municipality supplied utilities (water, wastewater, reuse water and natural gas) for hydronic HVAC water heating, potable and non-potable water use. The present invention takes advantage of new horizontal “trenchless” boring capabilities, but can also be used with trenched technology for installation. The present invention uses the inherent characteristics of a wastewater pressure sewer lateral pipe, potable water, and reuse water service connection piping design to co-install and provide thermal benefit to a geothermal HVAC in-ground piping loop system.